JP5717240B2 - Communication system and communication apparatus - Google Patents

Description

  The present invention relates to a communication system and a communication device in which a plurality of communication devices such as an ECU (Electronic Control Unit) mounted on a vehicle transmit and receive data via a common communication line (bus).

  Conventionally, a vehicle is equipped with a plurality of electronic devices to perform various processes. A plurality of ECUs are mounted on the vehicle to control the operation of these electronic devices. In order to operate a plurality of ECUs in a coordinated manner, each ECU is connected to each other via a network, and data is transmitted and received so that the plurality of ECUs share information. CAN (Controller Area Network) (see Non-Patent Document 1 and Non-Patent Document 2) is widely adopted as a communication protocol.

  Under the CAN convention, a plurality of ECUs are connected to a bus composed of a twisted pair cable that transmits an operation signal, and each ECU transmits and receives digital data represented by the operation signal. CAN is a protocol for serial communication, and only one ECU of a plurality of ECUs connected to the CAN bus can transmit data, and the other ECU terminates data transmission by one ECU. It is controlled to wait until it does. Further, when a plurality of ECUs transmit data simultaneously, arbitration is performed based on the ID attached to the data, and control is performed to transmit data with high priority.

ISO 11898-1: 2003 Road vehicles--Controller area network (CAN)-Part 1: Data link layer and physical signaling ISO 11519-1: 1994 Road vehicles--Low-speed serial data communication--Part1: General and definitions

  In recent years, along with the enhancement of electronic control performed in vehicles, the number of ECUs mounted on vehicles has increased, and the number of mounted ECUs has increased. The frequency of occurrence is increasing. For this reason, at the communication speed (about 1 Mbps) of the communication system according to the conventional CAN protocol, the amount of data that can be transmitted and received is not sufficient, and the current in-vehicle communication system is reaching the limit of the communication capacity.

  On the other hand, a protocol such as FlexRay has been proposed as a communication protocol for realizing an increase in communication speed. By adopting such another protocol, it is possible to increase the communication speed. However, changing the entire existing communication system from the CAN protocol to another protocol can reduce the development cost of the device and the reliability of the system. The burden is large.

  Therefore, it is required to create a mechanism that allows a conventional CAN communication system to be gradually changed from a place where high-speed communication is required to a high-order protocol compatible with CAN. It becomes possible to eliminate the problems related to the development cost and reliability as much as possible.

  Factors that limit the improvement in communication speed in the conventional CAN protocol include a processing time required for arbitration performed when a plurality of ECUs transmit data simultaneously. For example, in order to perform arbitration, each communication device outputs a signal related to its transmission data to the bus and then checks whether there is a change in the signal on the bus due to a collision with a signal output by another communication device. Although it is detected, it is necessary to detect the signal after a certain waiting time in consideration of a propagation delay of a signal output from another communication apparatus. The waiting time at this time hinders improvement in communication speed.

  The present invention has been made in view of such circumstances, and the object of the present invention is to eliminate the limiting factors related to speed improvement such as arbitration processing time based on the CAN protocol, and to the bus. An object of the present invention is to provide a communication system and a communication device that can speed up data transmission / reception performed by a plurality of connected communication devices.

The communication system according to the present invention is a communication system in which three or more communication devices are connected by a common communication line, and a plurality of communication devices receive a message transmitted by one communication device. One or a plurality of transmission rights are pre-assigned, and the three or more communication devices cyclically transmit messages in the order determined for each transmission right. A message transmission means for generating and transmitting a message including a plurality of reception success / failure information each indicating success / failure of message reception related to the right and data to be transmitted to another communication device; and a message received from the other communication device. and message retransmission means for re-transmitting the message according to the reception success or failure information included, without sending the message over a predetermined cycle after startup, the predetermined If a message is received from another communication device during the cycle, the subsequent message transmission is performed in synchronization with the message. If no message is received from the other communication device during the predetermined cycle, message transmission is performed. And communication start means for starting message transmission / reception with another communication device .

In the communication system according to the present invention, the communication device has time measuring means for measuring a waiting time until message transmission, and the communication start means of the communication device performs the message transmission or the predetermined cycle. If an abnormal message is received from another communication device during
After the waiting time corresponding to the assigned transmission right is timed by the time measuring means, the message is transmitted, and the plurality of communication devices time different waiting times by the time measuring means. It is characterized by the above.

The communication system according to the present invention includes a communication system in which three or more communication devices are connected by a common communication line, and a plurality of communication devices receive a message transmitted by one communication device. One or a plurality of transmission rights are pre-assigned to the three, the three or more communication devices cyclically transmit messages in the order determined for each transmission right, A plurality of reception success / failure information indicating success / failure of message reception related to each transmission right, and message transmission means for generating and transmitting a message including data to be transmitted to another communication device, received from another communication device A message resending means for resending the message in accordance with the reception success / failure information included in the message; a timing means for timing a waiting time until the message is sent; A communication resumption means for resuming message transmission after measuring the waiting time according to the assigned transmission right when the message is not received from another communication device during the cycle, The communication device is configured to time different waiting times by the time measuring means.

The communication system according to the present invention includes a communication system in which three or more communication devices are connected by a common communication line, and a plurality of communication devices receive a message transmitted by one communication device. One or a plurality of transmission rights are pre-assigned to the three, the three or more communication devices cyclically transmit messages in the order determined for each transmission right, A plurality of reception success / failure information indicating success / failure of message reception related to each transmission right, and message transmission means for generating and transmitting a message including data to be transmitted to another communication device, received from another communication device Message resending means for resending the message according to the reception success / failure information included in the message, and a communication stop for sending the message requesting to stop the message transmission. Stop request transmitting means, communication stop request receiving means for receiving a message requesting stop of communication processing from another communication device, and communication stop request receiving means from a plurality of other communication devices over a predetermined cycle. And a communication stop control means for stopping message transmission when a message requesting to stop processing is received.

Further, in the communication system according to the present invention, the message transmission means of the communication device may set other transmission right to be transmitted in one cycle from the previous message transmission related to the one transmission right to the current message transmission. The success or failure of receiving the message is included in the message to be transmitted as the reception success / failure information.

In addition, the communication system according to the present invention is configured so that each communication device transmits or receives a message related to the next communication right when the message related to one communication right is not transmitted for a predetermined time. It is characterized by being.

In the communication system according to the present invention, the message transmission unit of the communication device generates and transmits a message including identification information for identifying the transmission right, and each communication device receives the received message. The message transmission / reception synchronization is performed based on the identification information.

In the communication system according to the present invention, the message transmission means of the communication device generates and transmits a message including information for detecting or correcting an error in the identification information. .

In the communication system according to the present invention, the communication device includes an error counter that counts the number of error occurrences related to message transmission / reception, and the message transmission unit of the communication device generates an error occurrence counted by the error counter. When the number exceeds a predetermined value, the frequency of message transmission is reduced.

In the communication device according to the present invention , one or a plurality of transmission rights are assigned in advance in a communication device that transmits and receives messages to and from two or more other devices via a common communication line. Message transmission for generating and transmitting a message including a plurality of pieces of reception success / failure information indicating success / failure of message reception related to each transmission right including transmission right assigned to another device and data to be transmitted to the other device Means, a message retransmission means for retransmitting a message in accordance with reception success / failure information included in a message received from another device, and no message transmission over a predetermined cycle after activation. Between other devices
When a message is received, subsequent message transmission is performed in synchronization with the message, and when no message is received from another device during the predetermined cycle, message transmission is performed and message transmission / reception with the other device is performed. The message transmission means and the message retransmission means cyclically transmit messages to and from the other devices in the order determined by the assigned transmission right. It is characterized by the above.

In the communication device according to the present invention, one or a plurality of transmission rights are assigned in advance in a communication device that transmits and receives messages to and from two or more other devices via a common communication line. Message transmission for generating and transmitting a message including a plurality of pieces of reception success / failure information indicating success / failure of message reception related to each transmission right including transmission right assigned to another device and data to be transmitted to the other device Means, a message resending means for resending a message according to reception success / failure information included in a message received from another device, a communication stop request sending means for sending a message requesting to stop the message sending, and others Communication stop request receiving means for receiving a message for requesting stop of communication processing from the device, and a plurality of other devices over a predetermined cycle If the signal stop request receiving means receives a message requesting the stop of the communication processing, and a communication stop control means for stopping message transmission, the message transmission means and said message retransmission means, allocated transmission rights The messages are transmitted cyclically with the other devices in the order determined in (1).

In the present invention, in a network configuration in which a plurality of communication devices are connected by a common communication line (bus), one or more transmission rights (hereinafter referred to as slots) are assigned in advance to each communication device, and each communication device itself In this slot, messages are transmitted cyclically in a predetermined order. As a result, a plurality of communication devices use a bus in a time-sharing manner in a predetermined order to transmit data, so that a plurality of communication devices can transmit data simultaneously as in the conventional CAN protocol. There is no need to do arbitration. Therefore, there is no restriction on the time required for arbitration, and the communication speed can be increased.
In addition, when each communication device performs message transmission related to one slot, the message includes a plurality of reception success / failure information indicating success / failure of message reception related to other slots and data to be transmitted to other communication devices. Create and send. If there is no data to be transmitted to another communication device, a message including reception success / failure information and no data may be created and transmitted. By adopting a configuration for transmitting a message including reception success / failure information and data, each communication device can effectively utilize the slot given to itself to notify other communication devices of the success or failure of message reception, and , It is possible to give the data it has to other communication devices.
A message transmitted by one communication device is received by all other communication devices connected to the bus. Each communication device that has received the message can acquire the data included in the message, and can determine whether or not the message transmitted by itself has been correctly received from the reception success / failure information included in the message. . Therefore, each communication device checks the reception success / failure information included in the message received during one cycle from the previous message transmission related to one slot to the next message transmission related to this slot, and the message transmitted last time is If not correctly received, the message can be retransmitted when the next transmission opportunity for the same slot is given.
As a result, a plurality of communication devices can efficiently and efficiently perform message transmission without performing arbitration as in the conventional CAN protocol, and without causing message transmission to collide. Even if it is a case, the message can be reliably retransmitted.

  In the present invention, the message created by each communication device includes success / failure of message reception related to other slots transmitted / received in one cycle from the previous message transmission related to one transmission right to the current message transmission. Is included as reception success / failure information. That is, reception success / failure information for the total number of slots in the communication system is included in the message as information for one cycle (however, reception success / failure information for its own slot can be omitted. In this case, the total number of slots -1 information is included in the message). In this way, each communication device transmits the reception success / failure information for one cycle and receives the reception success / failure information transmitted from the other communication devices for one cycle. It is possible to know whether or not the own transmission message is correctly received by the communication device.

  Further, in the present invention, if the message transmission related to this slot is not performed after reaching the transmission order of the message related to one slot, the processing of the communication device to which this slot is allocated is for some reason (for example, trouble such as failure) Alternatively, it is estimated that the operation is stopped by a sleep mode or the like. Therefore, when message transmission related to one slot is not performed for a predetermined time, each communication apparatus omits message transmission / reception processing related to this slot and performs message transmission / reception processing related to the next slot. As a result, the period during which no message is transmitted / received can be shortened as much as possible, which contributes to an increase in communication speed. Even when a spare slot is provided to add optional equipment to the communication system, the processing related to the spare slot can be omitted when the optional equipment is not added.

  In the present invention, identification information (for example, slot number) for identifying a slot is included in a message created by each communication device. In order to share the bus in a time-sharing manner, a plurality of communication devices participating in the communication system need to grasp which slot is using the bus and perform message transmission in synchronization. Therefore, each communication device synchronizes processing related to message transmission / reception in accordance with the reception timing of the slot number included in the received message. As a result, a plurality of communication devices can perform processing synchronously, and message transmission / reception can be reliably performed.

  In the present invention, the message created by each communication device includes identification information such as a slot number and information for performing error detection or correction of the identification information. In the conventional CAN protocol, information (CRC (Cyclic Redundancy Check) sequence) for error detection of the entire message is included in the message, but apart from this, error detection or correction only for the slot number or the like is included. Include information in the message. In this communication system, since a plurality of communication devices perform message transmission cyclically using the bus in time division, it is important to determine which slot the transmitted message belongs to. If an error occurs in identification information such as a slot number that can be used for this determination, there is a risk that the message transmission order may be broken. Therefore, by including information for error detection or correction of identification information in a message, it is possible to reliably perform cyclic message transmission / reception. Even when an error is detected in the entire message, it can be determined whether or not the error has occurred in the identification information, so that the processing related to the subsequent message retransmission can be easily performed.

Also, in the present invention, each communication device counts the number of errors that occurred during message transmission / reception with an error counter. If the number of error occurrences is large, there may be a failure of the communication device. Therefore, when the counted number of error occurrences exceeds a predetermined value, the communication device reduces the frequency of message transmission. The reduction in the frequency of message transmission can be realized by a method of transmitting a message only once every several cycles, for example, even when the transmission order is given cyclically. Further, if an error occurs even after the frequency of message transmission is reduced and the value of the error counter exceeds the upper limit value, the message transmission of the communication device may be stopped.
In this way, by controlling the message transmission according to the number of error occurrences, it is possible to prevent a message transmitted by a communication device in which a failure or the like has occurred from adversely affecting the processing of other communication devices. The reliability of the system can be improved.

In the present invention, a plurality of communication devices sharing a bus need to synchronize processing (particularly processing related to slots). Immediately after the communication system is activated by turning on the power or returning from the sleep state, etc., the plurality of communication devices are not synchronized, so each communication device first synchronizes with other communication devices after activation. After establishment, communication processing is started.
At this time, each communication device is devoted to receiving messages from other communication devices during a predetermined cycle immediately after activation, and when a message is received during a predetermined cycle, other communication devices that have already started communication Since it can be determined that the message exists, the subsequent message transmission is performed in synchronization with the received message in order to synchronize with the communication device, and the communication process is started. If a message is not received during a predetermined cycle, it can be determined that there is no other communication device that has already started communication, so that it sends a message and starts communication processing.
As a result, a plurality of communication devices can start communication processing synchronously after the communication system is activated.

However, it may be determined that a message has not been received during a predetermined cycle, and a plurality of communication devices may start message transmission simultaneously. In such a case, a plurality of messages collide on the bus. Other communication devices cannot receive normal messages. Therefore, in the present invention, after each communication device has a time measuring means, and when a message is transmitted or an abnormal message is received, the time waiting means according to the slot assigned to itself is timed by the time measuring means. , Send a message.
By setting the standby time according to the slot assigned to each communication device, the plurality of communication devices of the communication system time each different time by the time measuring means. Therefore, after a message collision occurs, the communication device set with the shortest standby time performs the next message transmission alone, and other communication devices can normally receive and synchronize with this message. .

In addition, after the communication system is activated and synchronization between communication apparatuses is established, there is a possibility that a synchronization shift may occur in one or a plurality of communication apparatuses due to a communication failure or the like. Therefore, in the present invention, when each communication device has a time measuring unit and does not receive a message from another communication device over a predetermined cycle such as two cycles, the standby time corresponding to the slot assigned to itself is counted. After timing by means, the message is transmitted.
By setting the standby time according to the slot assigned to each communication device, the plurality of communication devices of the communication system time each different time by the time measuring means. Therefore, even when the messages transmitted by a plurality of communication devices collide due to a shift in synchronization and each communication device does not receive a message from another communication device, the shortest waiting time is reached. The set communication device performs the next message transmission alone, and other communication devices can normally receive and synchronize with this message.

  Further, in the present invention, when the communication system shifts to a power saving operation state such as a sleep mode, each communication apparatus transmits a request to stop message transmission (sleep request) to another communication apparatus, A sleep request is received from the communication device. Thereafter, when a sleep request is received from a plurality of communication devices in the communication system over a predetermined cycle, each communication device stops message transmission and transitions to the sleep mode. As a result, after a plurality of communication devices in the communication system are prepared for the transition to the sleep mode, the plurality of communication devices can be aligned and shift to the sleep mode.

  In the case of the present invention, when a slot is allocated to a plurality of communication devices connected to the bus, each communication device cyclically transmits a message in a predetermined order, and the message transmission related to one slot is performed. When a message including reception success / failure information indicating success / failure of message reception related to another slot and data to be transmitted to another communication device is created and transmitted, and the message is received, it is included in this message By adopting a configuration in which retransmission processing is performed according to reception success / failure information, it is not necessary to perform arbitration of the conventional CAN protocol, so that the communication speed between a plurality of bus-connected communication devices can be increased.

It is a block diagram which shows the hardware constitutions of the communication system and communication apparatus which concern on this invention. It is a block diagram which shows the function structure of the communication apparatus which concerns on this invention. It is a schematic diagram for demonstrating the outline | summary of the communication protocol of the communication system which concerns on this invention. It is a schematic diagram which shows the structure of the message used with the communication protocol of the communication system which concerns on this invention. It is a schematic diagram for demonstrating the response process which the communication system which concerns on this invention performs. It is a schematic diagram for demonstrating the response process which the communication system which concerns on this invention performs. It is a schematic diagram for demonstrating action point offset time, idle slot time, and maximum transmission slot time. It is a schematic diagram for explaining the basic operation of slot management by the slot management means. It is a schematic diagram for explaining the basic operation of slot management by the slot management means. It is a timing chart for explaining the synchronization processing of the slot counter by the slot management means. It is a schematic diagram for demonstrating the success or failure determination of the message transmission by a protocol control means. It is a schematic diagram for demonstrating the message retransmission process by a protocol control means. It is a schematic diagram for demonstrating the message retransmission process by a protocol control means. 6 is a chart showing a list of communication errors detected in the communication system according to the present invention. It is a graph which shows the fluctuation conditions of an error counter. It is a state transition diagram for demonstrating operation | movement of an error control means. It is a state transition diagram for demonstrating the operation | movement which concerns on the communication control process of ECU. It is a flowchart which shows the process sequence of ECU in an initial state. It is a flowchart which shows the process sequence of ECU in a synchronous preparation state. It is a flowchart which shows the process sequence of ECU in a synchronous preparation state. It is a flowchart which shows the process sequence of ECU in a synchronization waiting state. It is a flowchart which shows the process sequence of ECU in a synchronous state. It is a flowchart which shows the process sequence of ECU in a synchronous state. It is a flowchart which shows the process sequence of ECU in a sleep preparation state. It is a flowchart which shows the process sequence of ECU in a bus-off state. It is a flowchart which shows the process sequence of ECU in a bus sleep state. It is a timing chart which shows the example of a process of a startup sequence. It is a timing chart which shows the example of a process of a startup sequence. It is a timing chart which shows the example of a process of a startup sequence. It is a timing chart which shows the example of a process of a resynchronization sequence. It is a timing chart which shows the example of a process of a resynchronization sequence. It is a schematic diagram which shows the message structure of the communication system which concerns on a modification.

Hereinafter, the present invention will be specifically described with reference to the drawings showing embodiments thereof.
<Configuration of communication system>
FIG. 1 is a block diagram showing a hardware configuration of a communication system and a communication apparatus according to the present invention. In the figure, reference numeral 1 denotes an ECU (communication device), and a plurality of ECUs 1 are arranged at appropriate positions of a vehicle (not shown). Each ECU 1 controls various electronic devices mounted on the vehicle or detects the running state of the vehicle by sensors. Etc. are performed respectively. The plurality of ECUs 1 are connected to a common communication line (bus) 5 laid in the vehicle and can send and receive messages via the bus 5.

  The bus 5 has the same configuration as that of the bus used in the conventional CAN protocol, and is configured by a twisted pair cable that transmits an operation signal. A signal transmitted on the bus 5 is represented by a dominant value “dominant” corresponding to the logical bit “0” and a recessive value “recessive” corresponding to the logical bit “1”. However, in the communication system according to the present invention, dominant and recessive signal values are not necessarily treated as dominant values and inferior values, but the same signal values are used in order to maintain compatibility with the conventional CAN protocol.

  Each ECU 1 that is a component of the communication system is connected to a sensor that detects a traveling state of the vehicle and the like, an input unit 12 that acquires a signal input from the sensor, and an electronic device (a control target mounted on the vehicle) An output unit 13 connected to (not shown) and outputting a control signal, a storage unit 14 for storing programs and data necessary for control, a power supply circuit 15 for supplying power to each unit in the ECU 1, and a bus 5 And a communication unit 16 that transmits and receives data, and a control unit 11 that controls the operation of each unit in the ECU 1. In FIG. 1, only one ECU 1 shows a detailed internal configuration, and the other ECUs 1 have the same configuration, and therefore the detailed internal configuration is not shown.

The input unit 12 of the ECU 1 is connected to various sensors that detect, for example, the vehicle speed, acceleration, engine temperature, steering angle of the steering wheel, and the like of the vehicle, and detection values from the sensors are input as signals. The input unit 12 acquires the detection value detected by the sensor, stores it in the storage unit 14, and notifies the control unit 11 of the completion of acquisition of the detection value from the sensor. The output unit 13 is connected to an electronic device for electronically controlling various devices such as a vehicle engine or a brake, and the output unit 13 controls the operation of the various devices according to the control of the control unit 11. Is output. The ECU 1 may be configured to include only one of the input unit 12 and the output unit 13.

  The storage unit 14 is composed of a nonvolatile memory element that can rewrite data such as an EEPROM (Electrically Erasable Programmable Read Only Memory) or a flash memory. The storage unit 14 stores in advance programs, data, and the like that are executed by the control unit 11, and when the ECU 1 is turned on, the ECU 1 reads these programs, data, and the like from the storage unit 14 and starts processing. The storage unit 14 stores various data generated in the process of the control unit 11, detection values detected by the sensors, data transmitted to other ECUs 1 through communication, data received from other ECUs 1, and the like. The storage unit 14 may have a configuration in which a so-called ROM and RAM (Random Access Memory) are provided separately.

  The power supply circuit 15 is connected to a power supply source (not shown) such as an alternator or a battery of the vehicle, adjusts the power from the power supply source to a voltage or current suitable for each part, and then supplies the power to each part.

  The communication unit 16 is connected to the bus 5, reads data for transmission from the storage unit 14 under the control of the control unit 11, creates a message with predetermined information added to the data, and outputs the message to the bus 5. To send a message. The communication unit 16 receives a message transmitted from another ECU 1, extracts necessary data from the received message, stores it in the storage unit 14, and notifies the control unit 11 of completion of reception. In addition, the communication unit 16 performs various control processes related to communication. For example, a control process for transmitting and receiving messages in a time-sharing manner in synchronization with other ECUs 1 and messages from other ECUs 1. Various processes such as a process of determining success or failure of reception, a process of performing a response to the reception of a message from another ECU 1, or a process of retransmitting its own message according to the content of the message received from the other ECU 1 Is going. Details of message transmission / reception processing performed by the ECU 1 will be described later.

  The control unit 11 acquires information based on the signal input to the input unit 12 and the information received from the other ECU 1 via the bus 5 and performs a calculation based on the acquired information to generate a control signal. The electronic device mounted on the vehicle is controlled by outputting a control signal from the output unit 13. At this time, when the control unit 11 needs to share information from the sensor or the like input to the input unit 12 or a calculation result with other ECUs 1, the control unit 11 generates a message including the information as data, and the communication unit 16. To other ECU1.

<Functional configuration of communication device>
FIG. 2 is a block diagram illustrating a functional configuration of the communication apparatus according to the present invention, and illustrates a configuration related to a communication function realized by the control unit 11 and the communication unit 16 of the ECU 1. The function of the ECU 1 can be divided into an application layer, a protocol control layer, and a physical layer. The application layer includes one or a plurality of application software (hereinafter referred to as applications) 101. The protocol control layer includes protocol control means 102, error control means 103, message generation means 104, slot management means 105, bit sampling means 106, and the like. The physical layer is composed of a bus driver 107 and the like.

  The physical layer is a layer related to physical connection with the bus 5 and transmission / reception of electric signals to / from the bus 5, and corresponds to a physical layer of an OSI (Open Systems Interconnection) reference model. The physical layer bus driver 107 outputs a signal corresponding to the value (dominant / recessive) of the transmission message given from the protocol control layer to the bus 5 and detects the signal level of the bus 5 to detect the dominant / recessive level. Convert to value and give to protocol control layer. The bus driver 107 is provided in the communication unit 16.

  The application layer is a layer that provides a specific service related to the control of the electronic device mounted on the vehicle, and corresponds to the application layer of the OSI reference model. Each application 101 in the application layer exchanges information with the protocol control layer using a predetermined API (Application Programming Interface). The application 101 is realized by the control unit 11 executing the program and data stored in the storage unit 14.

  The bus driver 107 in the physical layer and the application 101 in the application layer of the ECU 1 according to the present embodiment can have substantially the same configuration as that provided in the conventional CAN protocol. The communication device according to the present invention and the conventional CAN protocol communication device have different protocol control layer configurations and different communication protocols. However, the communication protocol of the communication apparatus according to the present invention is an improvement based on the conventional CAN protocol.

  The communication protocol of the communication system according to the present invention is preferably used in a bus connection network in which a plurality of communication devices as shown in FIG. 1 are connected to a common communication line. However, it can also be used in networks having other configurations. For example, even in a network having a configuration in which a plurality of communication devices are star-connected mainly around a gateway, communication processing performed between the gateway and the communication device is performed according to the present invention. This can be done with a communication protocol. Further, in the communication protocol of the present invention, there is no hierarchical relationship such as master / slave among a plurality of communication devices that perform communication, and all communication devices communicate in an equal relationship.

  In the conventional CAN protocol, when a plurality of communication devices simultaneously transmit messages to the bus, arbitration processing (arbitration) according to the priority of an ID (IDentifier) included in the message is performed in each communication device. The message with the highest priority is sent. In contrast, the arbitration is not performed in the communication protocol of the present invention. In the communication protocol of the present invention, the plurality of ECUs 1 connected to the bus 5 cyclically transmit messages (that is, periodically transmit messages in a predetermined order), so that the bus 5 is time-shared. Use it to avoid collision of message transmissions.

<Outline of communication protocol>
FIG. 3 is a schematic diagram for explaining the outline of the communication protocol of the communication system according to the present invention. In the following description, a configuration in which four ECUs 1 are connected to the bus 5 is assumed, and the four ECUs 1 are distinguished by reference numerals 1a to 1d, respectively. In the communication protocol of the present invention, one or a plurality of slots (slot numbers) are assigned in advance (statically) to the ECUs 1a to 1d participating in the communication. The slot indicates a transmission right when the message is transmitted cyclically. The smaller the slot number, the earlier the transmission order. In addition, duplication of slot numbers is not recognized, and only one ECU 1a to 1d can perform transmission for one slot number.

  For example, as shown in FIG. 3A, slot 1 and slot 5 are assigned to ECU 1a, slot 2 is assigned to ECU 1b, slot 3 and slot 6 are assigned to ECU 1c, and slot 4 is assigned to ECU 1d. Assigned. Each ECU 1a to 1d is preliminarily given common information such as the total number of slots in the network and the maximum time (one slot time) that the bus 5 can be used for one message transmission related to one slot. ing.

  Each of the ECUs 1a to 1d transmits a message in order from the ECUs 1a to 1d to which slots having a smaller number are assigned, with the total number of slots × 1 slot time as one cycle. For example, as shown in FIG. 3B, the ECU 1a to which the slot 1 is assigned transmits the message A (abbreviated as Msg in the figure) A first, and the ECU 1b to which the slot 2 is assigned sends the message B second. ECU 1c to which slot 3 is assigned transmits message C third, and ECU 1d to which slot 4 is assigned transmits message D fourth. Thereafter, the ECU 1a assigned the slot 5 transmits the message E fifth, and the ECU 1c assigned the slot 6 transmits the message F sixth. One cycle is completed when the message transmission related to the slot with the largest number is completed, and the ECU 1a to which the slot 1 is assigned transmits the message G in the next cycle.

  As described above, since the plurality of ECUs 1a to 1d connected to the bus 5 perform the cyclic message transmission according to the slot number, the plurality of messages do not collide on the bus 5. It is not necessary for each ECU 1a to 1d to perform arbitration of the conventional CAN protocol. For this reason, when transmitting a message in the conventional CAN protocol, the communication device needs to detect the presence or absence of a signal change on the bus for each bit after outputting the message to the bus. There is no need to perform such detection processing for each bit, and the communication speed can be increased. The control of message transmission / reception by the slots as described above is performed by the protocol control means 102 and the slot management means 105 of each ECU 1a to 1d.

  Messages transmitted from any of the ECUs 1 a to 1 d can be received by all the other ECUs 1 a to 1 d connected to the bus 5. The other ECUs 1a to 1d that have received the message perform a response (so-called ACK (ACKnowledgement) / NAK (Negative AcKnowledgement) transmission) as to whether or not the message has been correctly received, to the ECUs 1a to 1d that have transmitted the message. There is a need. In the conventional CAN protocol, a response is made by using a 1-bit ACK slot included in the message, and the communication device that sent the message detects the signal change during the ACK slot period, so that the message is received correctly. It can be determined whether or not.

  Since the communication protocol of the present invention does not detect a signal change for each bit at the time of message transmission as described above, the message reception response is performed by a method different from the conventional CAN protocol. For this reason, in the communication protocol of this invention, the structure of the message transmitted / received between ECU1a-1d shall be extended in several points with respect to the message structure of the conventional CAN protocol.

<Message generation>
Next, the operation of the message generation unit 104 included in the protocol control layer of the ECU 1 will be described. FIG. 4 is a schematic diagram showing the structure of a message used in the communication protocol of the communication system according to the present invention, which is generated by the message generation means 104 of the ECU 1. In the communication protocol of the present invention, two types of messages, a data frame and an ACK frame, are used. The data frame of the communication protocol of the present invention corresponds to the data frame of the conventional CAN protocol, and the ACK frame of this protocol does not correspond to the conventional CAN protocol. The data frame is for performing transmission of data to other ECUs 1 and a response related to success or failure of data reception. The ACK frame is used when there is no data to be transmitted to the other ECU 1, and is used when starting up the communication system and performing sleep.

  The data frame of this communication protocol includes an SOF (Start Of Frame), an ID field, a control field, a sleep bit, an error active bit (abbreviated as EA in FIG. 4), an ACK field, and a slot number field (slot in FIG. 4). ), A data field, a CRC (Cyclic Redundancy Check) field, and an EOF (End Of Frame). The ACK frame has a configuration in which the data field is removed from the data frame. The SOF, control field, data field, EOF, and IFS are the same as those of the conventional CAN protocol.

  The SOF is the same as the SOF provided in the data frame of the conventional CAN protocol. This bit represents the start of the message and is a 1-bit dominant. Each ECU 1 of the communication system performs message reception in synchronization by detecting the SOF on the bus 5.

  The ID field has the same configuration as the arbitration field provided in the data frame of the conventional CAN protocol. However, since the arbitration is not performed in the communication protocol of the present invention as described above, the value of this field is simply used as the message ID. Used. The ID field includes ID data and RTR (Remote Transmission Request) bits. ID data indicates the type of message, which is 11 bits in the standard format and 29 bits in the extended format. The RTR is 1-bit data and is the same as the conventional CAN protocol.

  The control field is the same as the control field of the conventional CAN protocol, and is an IDE (IDentifier Extension) bit for distinguishing a standard format or an extended format, and a 4-bit DLC (data length code indicating the data length of the data frame) ) Etc. are included. Note that the ID data in the ID field is used to identify the data frame and the ACK frame by each of the ECUs 1a to 1d, and a frame that is normally received with ID data = 1 is an ACK frame (however, the value of this ID data is an example) And other values may be used). The ECUs 1a to 1d perform transmission by setting DLC = 0 in the ACK frame. When the ECUs 1a to 1d receiving the ACK frame receive the frame of ID data = 1, the received frame is DLC ≠ 0. Even so, the reception process is performed assuming that DLC = 0.

  The sleep bit is 1-bit information used for processing related to sleep in the communication system, and is used only in the ACK frame. When the sleep bit is set to dominant, a normal operation is performed, and when the sleep bit is set to recessive, an ACK frame is received as a sleep request, and processing related to sleep is started. In the data frame, the sleep bit is always set to dominant.

  The error active bit is 1-bit information, and is used to notify an error state when an error relating to communication processing occurs. When the error active bit is set to dominant, the error state is error active, and when the error active bit is set to recessive, the error state is error passive (details such as error active and error passive are described later). To do).

  The ACK field is information of the number of bits equal to the total number of slots in the communication system, and one slot is associated with each bit, and success / failure information of message reception for one cycle is set. For example, when the total number of slots is 16, the ACK field is 16-bit information, slot 1 reception success / failure information is set in the first bit, slot 2 reception success / failure information is set in the second bit,. Reception success / failure information of slot 16 is set in the bit. As for the value of each bit in the ACK field, recessive corresponds to reception success (ACK), and dominant corresponds to reception failure (NAK).

  However, since the communication system of the present invention does not require functions such as arbitration and ACK bit of the conventional CAN protocol, the dominant can correspond to ACK and the recessive can correspond to NAK. That is, the combination of ACK and NAK in the ACK field, recessive and dominant is not particularly limited as long as it is unified within the communication system, and any combination may be used.

  The slot number is set to the number of the slot in which this message transmission is performed, and is used for each ECU 1 of the communication system to perform synchronization correction (details will be described later). The data size of the slot number is defined by the total number of slots. For example, if the total number of slots is 16, the slot number is 4-bit information.

  The data field is the same as the data field provided in the data frame of the conventional CAN protocol. The data field is composed of 0 to 8 bytes of data and is transmitted MSB (Most Significant Bit) first. Each ECU 1 transmits arbitrary data to be transmitted to other ECUs 1 in this data field.

  The CRC field is composed of a 15-bit CRC sequence and a 1-bit CRC delimiter (delimiter bit), and is used for error detection of the received message. The CRC sequence can be acquired by performing an operation using a predetermined generator polynomial for values from the SOF to the data field. The generator polynomial used for the calculation may be the same as that used in the conventional CAN protocol. The ECU 1 that has received the message can perform error detection by comparing the value calculated by the generator polynomial for the received message with the value of the CRC sequence of the received message, and if the two values do not match Judge that an error has occurred. The CRC delimiter is 1 bit recessive in the conventional CAN protocol, but in the communication protocol of the present invention, the CRC delimiter is 2 bits in total: 1 bit recessive and 1 bit dominant. Although the length of the CRC sequence is 15 bits, the length is not limited to this, and may be 14 bits or less or 16 bits or more.

  The EOF is the same as the EOF provided in the data frame of the conventional CAN protocol. This bit represents the end of the data frame and is 7 bits recessive.

  The data frame and the ACK frame described above are generated by the message generation unit 104 of the ECU 1 according to the control of the protocol control unit 102. The message generation unit 104 outputs the message to the bus 5 by giving the generated message to the bus driver 107 via the bit sampling unit 106, and transmits the message to all other ECUs 1 connected to the bus 5. Further, the message generation means 104 extracts the data of each field shown in FIG. 4 from the sampling result given from the bit sampling means 106, that is, the received message, and gives it to the protocol control means 102.

  5 and 6 are schematic diagrams for explaining response processing performed by the communication system according to the present invention. FIG. 5 shows an example of message transmission in the communication system, and FIG. 6 shows the contents of the ACK field included in each message. The examples shown in FIGS. 5 and 6 are based on the configuration of the communication system shown in FIG. 3A (a configuration in which four ECUs 1a to 1d transmit messages using six slots). is there.

  As shown in FIG. 5, when each of the ECUs 1a to 1d of the communication system is activated and communication is started, transmission of a message is started from the ECU 1a to which slot 1 is assigned, and a plurality of ECUs 1a to 1d are arranged in the slot number order. Send a message. In the illustrated example, the ECU 1a to which the slot 1 is assigned transmits the message A, the ECU 1b to which the slot 2 is assigned transmits the message B, the ECU 1c to which the slot 3 is assigned transmits the message C, and the slot 4 The assigned ECU 1d transmits the message D, the ECU 1a to which the slot 5 is assigned transmits the message E, the ECU 1c to which the slot 6 is assigned transmits the message F, and one cycle is completed. In the next cycle, ECU 1a to which slot 1 is assigned transmits message G, ECU 1b to which slot 2 is assigned sends message H, ECU 1c to which slot 3 is assigned sends message I, and the same processing Is repeated.

  As shown in FIG. 6, the messages transmitted by the ECUs 1a to 1d include 6-bit (= slot number) information (ACK1 to ACK6) as ACK fields. Success or failure is set as 1-bit recessive (ACK) or dominant (NAK) in ACK1 to ACK6, respectively. Each of the ECUs 1a to 1d transmits a message by setting ACK to the bit of the ACK field for the slot allocated to itself.

  Immediately after the communication system starts communication, the ECUs 1a to 1d have not yet sent and received messages, and the ECUs 1a to 1d have not received messages. As described above, in one cycle immediately after the start of communication, each ECU 1a to 1d transmits a message by setting ACK to the bit of the ACK field related to the slot where the message transmission / reception is not performed.

  In communication related to slot 1 in the first cycle after the start of communication, ECU 1a sets ACK in ACK1 and ACK5 corresponding to slot 1 and slot 5 allocated to itself, and does not transmit / receive messages. A message A in which ACK is set in ACKs 2 to 4 and 6 corresponding to 2 to 4 and 6 is created and transmitted.

  Next, in the communication related to slot 2 in the first cycle, the ECU 1b sets the success / failure (ACK / NAK) of the reception related to the message A transmitted in the communication related to slot 1 to ACK1, and the slot 2 assigned to itself. ACK2 is set in ACK2 corresponding to, and message B in which ACK is set in ACK3 to ACK6 corresponding to slots 3 to 6 in which no message is transmitted / received is generated and transmitted.

  Next, in the communication related to the slot 3 in the first cycle, the ECU 1c sets the success / failure of the reception of the messages A and B transmitted in the communication related to the slot 1 and the slot 2 to ACK1 and ACK2, and is assigned to itself. ACK is set in ACK3 and ACK6 corresponding to slot 3 and slot 6, and message C in which ACK is set in slot 4 and slot 5 in which no message is transmitted and received is generated and transmitted.

  Similarly, transmission of the message D of the ECU 1d related to the slot 4 in the first cycle, transmission of the message E of the ECU 1a related to the slot 5, and transmission of the message F of the ECU 1c related to the slot 6 are performed. When message transmission / reception for one cycle is completed, each ECU 1a to 1d transmits at least one message, and the ECU 1a correctly transmits the message A transmitted in slot 1 of the first cycle to the other ECUs 1b to 1d. Whether or not the message has been received can be determined by examining the ACK fields of the messages B, C, D, and F from the other ECUs 1b to 1d and determining whether or not ACK is set for ACK1 of the message.

  When the ACK1 of all messages is set to ACK, the ECU 1a determines that the message A transmitted in the slot 1 is normally received by all the ECUs 1b to 1d, and in the slot 1 of the next cycle. A message G of other data is transmitted. On the other hand, if any ACK1 is set to NAK, the ECU 1a determines that the message A transmitted in the slot 1 is not normally received, and re-sends the message A in the slot 1 of the next cycle. Send. In the example illustrated in FIG. 6, the message A is normally received by all the other ECUs 1 b to 1 d.

  In communication related to slot 1 in the second cycle, the ECU 1a sets ACKs 2 to 4 and 6 as success or failure of reception of messages B to D and F related to slots 2 to 4 and 6 in the first cycle, and is assigned to itself. A message G in which ACK is set in ACK1 and ACK5 corresponding to the slots 1 and 5 is generated and transmitted.

  Similarly, the ECU 1b transmits itself in slot 2 of the first cycle by examining the ACK field of the message received during one cycle from slot 3 of the first cycle to slot 1 of the second cycle. It can be determined whether or not the message B is correctly received by the other ECUs 1a, 1c, and 1d. In communication related to slot 2 in the second cycle, when message B is correctly received, ECU 1b creates and transmits a new message H as shown in FIG. 6, and message B is not correctly received. Message B is retransmitted.

  Similarly, the ECU 1c transmits itself in slot 3 of the first cycle by examining the ACK field of the message received during one cycle from slot 4 of the first cycle to slot 2 of the second cycle. It can be determined whether or not the message C is correctly received by the other ECUs 1a, 1b, and 1d. In communication related to slot 3 in the second cycle, when the message C is correctly received, the ECU 1c creates and transmits a new message I as shown in FIG. 6, and the message C is not correctly received. Message C is retransmitted.

  As described above, each ECU 1a to 1d creates a message including data (data field) to be transmitted to the other ECUs 1a to 1d and information (ACK field) indicating success or failure of message reception from the other ECUs 1a to 1d. Then, this message is transmitted to all the ECUs 1a to 1d in the slot assigned to itself. Thereby, each ECU1a-1d can receive the message from all ECU1a-1d in 1 cycle, By checking the ACK field contained in each message, the message transmitted last time is all others. The ECUs 1a to 1d can determine whether or not the messages have been correctly received, and can determine whether or not to retransmit this message. Each of the ECUs 1a to 1d may transmit an ACK frame when there is no data to be transmitted to the other ECUs 1a to 1d in the slot assigned to itself.

  In the conventional CAN protocol, each communication device included in the communication system performs writing to the ACK slot included in the message output on the bus (processing to change from recessive to dominant), whereby the communication device that is the message transmission source Can determine the success or failure of message reception. The present invention enables the communication system to perform error detection equivalent to the conventional CAN protocol by performing a response to the message reception as described above in the protocol control layer of each ECU 1a to 1d. Regardless of whether the application 101 in the application layer is the conventional CAN protocol or the communication protocol of the present invention, the application 101 can perform processing related to communication in the same way. Development can be done without being conscious of whether

<Bit sampling>
Next, the operation of the bit sampling means 106 included in the protocol control layer of the ECU 1 will be described. In the communication system of the present invention, the signal on the bus 5 is treated as a binary signal represented by a dominant or recessive logic value, as in the conventional CAN protocol. The bit sampling means 106 provides binary data (that is, a message) obtained by periodically sampling the signal on the bus 5 to the message generating means 104 and the slot generating means 105, and protocol control is performed via these means. To the means 102.

  When a plurality of ECUs 1 connected to the common bus 5 perform message reception, it is necessary for all the ECUs 1 to perform reception processing in synchronization. The bit sampling means 106 also performs processing to synchronize with other ECUs 1 in response to signal changes on the bus 5. There are two types of synchronization by the bit sampling means 106: hard synchronization and resynchronization.

  In hard synchronization, when the signal on the bus 5 is in a recessive state for a predetermined period or longer, the bit sampling means 106 determines that the message is not being transmitted / received, and then the signal on the bus 5 changes from recessive to dominant. Synchronization is performed with respect to the timing of the change to (the SOF timing of the message). The bit sampling means 106 samples the signal value on the bus 5 using the edge of the SOF signal change as a synchronization point. The hardware synchronization by the bit sampling means 106 is the same processing as that performed by the conventional CAN protocol.

  In resynchronization, the bit sampling means 106 corrects synchronization in accordance with changes in bits other than those for which hardware synchronization is performed. The bit sampling means 106 compares the position of the signal change assumed by itself with the position of the signal change actually detected on the bus 5 to calculate an error, and corrects the sampling timing to cancel this error. . In the conventional CAN protocol, resynchronization is performed by both transmission and reception of a message. However, in the communication protocol of the present invention, the signal level of the bus 5 is not detected at the time of message transmission. Only when a message is received.

<Slot management>
Next, the operation of the slot management means 105 included in the protocol control layer of the ECU 1 will be described. The slot management means 105 of the ECU 1 manages slots assigned to each ECU 1 in advance so that the plurality of ECUs 1 can cyclically transmit messages as described above. In the communication protocol of the present invention, it is necessary for a plurality of ECUs 1 to know in common which slot is permitted to transmit a message at a certain point in time, and the slot management means 105 determines a slot for message transmission. Management processing for common knowledge, that is, slot synchronization processing is performed. Further, the slot management unit 105 performs slot management such as skipping this slot and transmitting / receiving a message related to the next slot when no message transmission is performed for a certain slot.

  In the communication protocol of the present invention, when it is detected that message transmission is not performed for a certain slot, each ECU 1 does not perform message reception processing for this slot, and moves to processing for the next slot, The message transmission / reception process related to the ECU 1 that has not transmitted a message due to a problem or the like is omitted, and communication is performed only by the ECU 1 that can perform message transmission.

  As a result, even if the ECU 1 in which a failure or the like has occurred in the communication system and the ECU 1 cannot transmit a message, the processing of the slot related to the ECU 1 can be omitted to avoid other problems in the communication system. The ECUs 1 can exchange messages with each other. In addition, a spare slot is provided to add the optional ECU 1 to the communication system, and the processing related to the spare slot can be omitted even when the optional equipment is not added.

  In order to realize the above processing, the slot management means 105 of each ECU 1 is preset with an action point offset time, an idle slot time, and a maximum transmission slot time for one slot time during which a message can be transmitted. It is determined that message transmission related to a slot assigned to another ECU 1 is not performed with a predetermined time as a reference, and processing for omitting message reception processing related to this slot is performed. FIG. 7 is a schematic diagram for explaining the action point offset time, the idle slot time, and the maximum transmission slot time.

  When each ECU 1 reaches the start time of the slot assigned to itself, it waits for a predetermined action point offset time, and then starts sending a message. The start point of message transmission in the slot is called an action point, and the time from the start point of the slot to the action point is the action point offset time.

  When each of the ECUs 1 has reached the start time of a slot assigned to another ECU 1 and the idle slot time has not elapsed and the message transmission related to this slot has not been made, the ECU 1 to which this slot is assigned is It is assumed that the message transmission is not performed due to the cause, and the communication processing related to the next slot is transitioned to.

  Each ECU 1 transmits a message from the start of the slot assigned to the ECU 1 until the maximum transmission slot time elapses. The message transmitted by each ECU 1 may have a variable length, but the message cannot be transmitted beyond the maximum transmission slot time. As a result, even when the ECU 1 continues to perform abnormal message transmission due to a failure or the like, the message transmission is stopped after the maximum transmission slot time is reached, and a transition is made to communication processing related to the next slot. .

These predetermined times are set in advance at the design stage of the communication system so as to satisfy the following conditions.
Idle slot time> Action point offset time + Frame detection confirmation time + RTT ± α
Maximum transmission slot time> Maximum transmission time of 1 frame + Action point offset time ± α

  In the above conditions, RTT (Round Trip Time) is the time required for a message to reciprocate between two ECUs. The frame detection confirmation time is a time required for another ECU 1 to recognize reception of a message after a message transmitted from one ECU 1 arrives at the other ECU 1, and is an internal delay of the communication unit 16 of the ECU 1. This includes the time and the time required to detect the signal change. Further, α is a margin that allows a cumulative amount of clock error between the plurality of ECUs 1.

  8 and 9 are schematic diagrams for explaining the basic operation of slot management by the slot management means 105. FIG. 8 shows a timing chart of signals used for slot management, and FIG. The definition is shown as a chart. Each ECU 1 includes an internal oscillator, and the internal operation clock output from the oscillator is Sample_clock (in FIG. 8, only the rising (or falling) edge of the operation clock is shown). Each part (each means) in the ECU 1 performs processing based on this operation clock. The plurality of ECUs 1 connected to the common bus 5 operate with operation clocks having substantially the same frequency. A signal indicating the sampling point of the received message by the bit sampling means 106 is Sample_point.

  The slot management means 105 has two counters, a bit counter (Slot_bit_cnt) and a slot counter (Slot_cnt). The bit counter is a counter indicating how many bits of a message to be transmitted / received are being processed. The bit counter is counted up for each sampling point of the bit sampling means 106 (detected when the value of Sample_point has changed to 1 (high level), see arrow (1) in the figure). .

  The slot counter of the slot management means 105 is a counter indicating a slot that has a right to transmit a message at the present time. The slot counter is counted up when Slot_cnt_ena is at a high level and the bit counter exceeds a predetermined value (the predetermined value is 2 in FIG. 8) (see arrow (2) in the figure). The value of the slot counter is initialized when Slot_cnt_ena is at a high level and the number of slots per cycle is exceeded.

  When the value of the slot counter changes, the signal Slot_cnt_point becomes a high level for one clock (see (3) in the figure), and the change of the slot is notified to each means in the ECU 1 by this signal. Further, the signal Slot_acpoint indicates an action point in the slot, and when a predetermined action point offset time (Slot_acpoint_bit) has elapsed from the start of the slot (in the example of FIG. 8, the action point offset time is 1 and the bit counter The signal Slot_acpoint becomes a high level for one clock (see the arrow (4) in the figure).

  The signal Slot_wrcnt and the signal Slot_wrcnt_cmd are signals input from the outside of the slot management unit 105 and are used for synchronization processing described later. The signal Slot_wrcnt is for the protocol control means 102 to give the slot management means 105 the slot number included in the normally received message. The signal Slot_wrcnt_cmd is used to instruct the timing at which the slot management means 105 writes (takes in) the slot number designated by the signal Slot_wrcnt.

  The slot management means 105 manages the slot number at which a message can be transmitted at the present time by counting up or initializing the value of the slot counter according to the values of the plurality of signals and the bit counter. In the plurality of ECUs 1 connected to the common bus 5, each slot management means 105 needs to share a slot number, and the slot management means 105 performs a synchronization process of the slot counter when receiving a message.

  FIG. 10 is a timing chart for explaining the slot counter synchronization processing by the slot management means 105. The signals shown in FIG. 10 are the same as those shown in FIGS. 8 and 9, and the signal Slot_cnt_ena_q is a signal obtained by delaying the signal Slot_cnt_ena by one clock. Since the bit count reaches a predetermined value at the timing indicated by the broken line (1) in the figure, the slot management means 105 increments the slot counter from slot 1 to slot 2. Thereafter, message reception from the other ECU 1 is started, and the slot management means 105 changes the signal Slot_cnt_ena from the high level to the low level at this timing, and the value of the slot counter is fixed (arrow (2) in the figure). reference).

  When the message reception process ends normally, the protocol control unit 102 notifies the reception end by the signal Slot_wrcnt_cmd. At this time, the slot number included in the normally received message is given as the signal Slot_wrcnt from the protocol control means 102 to the slot management means 105, and according to the timing of the reception end notification by the signal Slot_wrcnt_cmd, the slot management means 105 The given slot number is taken in and set in the slot counter (see arrow (3) in the figure). As a result, the slot counter is synchronized.

  In addition, the slot management unit 105 changes the signal Slot_cnt_ena to a high level after the notification of the reception end by the signal Slot_wrcnt_cmd is given, and permits the slot counter to be updated. When the signal Slot_cnt_ena_q changes from the low level to the high level, the value of the bit count is initialized (see the arrow (4) in the figure), and the value of the slot counter is incremented at the next sampling point (in the figure). Arrow (5)).

  Note that the slot management means 105 of each ECU 1 performs the synchronization process as described above each time a message is received. However, the synchronization process is not performed in the slot management means 105 of the ECU 1 that performs message transmission.

<Protocol control>
Next, the operation of the protocol control means 102 included in the protocol control layer of the ECU 1 will be described. As described above, in the communication protocol of the present invention, when a plurality of ECUs 1 connected to the common bus 5 synchronize slot numbers and slot times, each ECU 1 arrives at the transmission order of slot numbers assigned to itself. In this configuration, message collision is avoided by sending a message. The protocol control unit 102 performs message transmission / reception processing according to the slot number as shown in FIGS. 3, 5, 6 and the like, processing for setting ACK or NAK in the ACK field in the transmission message, and in the received message. The message is retransmitted according to the value of the ACK field. Further, the protocol control unit 102 has a synchronization shift between the plurality of ECUs 1 due to a process (startup sequence) in which the plurality of ECUs 1 synchronize with each other when starting the communication system or the like, and some communication failure. Resynchronization processing (resynchronization sequence) in this case, processing (sleep sequence) in the case of stopping the operation of the communication system, and the like.

  After each ECU 1 of the communication system is activated by power-on or the like, the protocol control means 102 executes a process for synchronizing the slot with another ECU 1 sharing the bus 5 as a startup sequence. In the start-up sequence, first, it is determined whether or not communication by another ECU 1 has already been started by checking the presence or absence of a signal on the bus 5, and if it is determined that communication has not started, the protocol control means 102 Prompts activation of another ECU 1 by starting its own message transmission. If it is determined that communication has already started, the protocol control unit 102 receives a message from another ECU 1 and performs subsequent communication processing in synchronization with the slot number included in the received message. .

  However, if a plurality of ECUs 1 determines that communication has not started, message transmissions by these plurality of ECUs 1 may collide. In such a case, the other ECU 1 that has received the collided message regards this message as being in slot 1 and performs communication processing for the next and subsequent slots, and the ECU 1 that has detected an abnormality in the subsequent communication processing corrects the processing. This suppresses the occurrence of further message collisions.

  In addition, after the message transmission / reception is normally started in the communication system, the synchronization of the message transmission / reception by the plurality of ECUs 1 in the communication system is performed by each ECU 1 performing the slot synchronization at the time of message reception as described above. However, there is a possibility that the slot number may be shifted due to some kind of communication failure. Each ECU 1 of the communication system continues the communication process even when such a deviation occurs, and the ECU 1 that detects an abnormality in the subsequent communication process performs the resynchronization process. The protocol control means 102 of each ECU 1 determines that a communication error has occurred when there is no normally received message between the slot transmitted by itself and the slot two cycles later, and the resynchronization sequence is determined. Run.

  Further, when the operation of the communication system is stopped to enter the low power consumption state (sleep mode), each ECU 1 of the communication system obtains an agreement with other ECUs 1 to enter the sleep mode, and then the sleep mode It is necessary to make a transition to Whether each ECU 1 shifts to the sleep mode is determined by the application 101 of the application layer. When the sleep request is given from the application 101 to the protocol control unit 102 of the protocol control layer, the protocol control unit 102 Process to obtain a consensus on migration. Specifically, the protocol control unit 102 to which the sleep request is given notifies the other ECU 1 of shifting to the sleep mode by transmitting an ACK frame in which the sleep bit is set to recessive. After that, the protocol control means 102 determines that an agreement to shift to the sleep mode has been obtained when the ACK frame having the sleep bit set to recessive is received for a predetermined cycle for all slots related to the other ECU 1, Transition to mode. That is, in this communication system, when all ECUs 1 are determined to shift to the sleep mode and the sleep bit is set to recessive in all the ACK frames transmitted by each ECU 1, all the ECUs 1 shift to the sleep mode. . On the other hand, if at least one ECU 1 determines not to shift to the sleep mode and the ECU 1 does not transmit an ACK frame with the sleep bit set to recessive, the ECU 1 in the communication system shifts to the sleep mode. There is no. The ECU 1 that has shifted to the sleep mode reduces power consumption by a method such as reducing the sampling frequency of the bit sampling by the bit sampling means 106 and is activated when a message transmitted from another ECU 1 is detected on the bus 5. (Wake up).

  The protocol control means 102 of each ECU 1 corresponds to the slot number as shown in FIG. 3, FIG. 5, FIG. 6, etc., except for performing exceptional processing such as the above startup sequence, resynchronization sequence and sleep sequence A message transmission / reception process, a process of setting ACK or NAK in the ACK field in the transmission message, a process of retransmitting the message according to the value of the ACK field in the received message, and the like are performed. The protocol control means 102 of each ECU 1 does not receive a message including a NAK response from another ECU 1 within one cycle after completion of its own message transmission, and receives an ACK response from at least one other ECU 1. When a message including “” is received, it is determined that the message transmitted by itself is normally received, and a new message is transmitted. On the other hand, when the protocol control means 102 receives one or more messages including a NAK response from another ECU 1 or does not receive any message including an ACK response, the protocol control means 102 normally transmits the message. Judge that it was not received and resend the message. Also, the protocol control unit 102 determines that the message transmitted by itself is not normally received even when an abnormal message that cannot determine ACK / NAK is received from another ECU 1, and retransmits the message.

  FIG. 11 is a schematic diagram for explaining the success / failure determination of message transmission by the protocol control means 102. FIG. 11 shows a case where the ECU 1 to which the slot 1 is assigned makes a message transmission success / failure determination in the communication system in which one slot is assigned to each of the six ECUs 1. 6 shows an ACK / NAK response result related to slot 1 included in the ACK field of the message received during the period 6.

  The protocol control means 102 of the ECU 1 to which slot 1 is assigned checks the value of ACK 1 in the ACK field included in the message received during the period from slot 2 to slot 6 after its own transmission, and ACK is set for all messages. If so, it is determined that the message transmission was successful (see case 1 in FIG. 11). Further, even when an ACK is set in a message received from at least one ECU 1 and no message is received from any other ECU 1, the protocol control means 102 determines that its own message transmission has succeeded (case 2 in FIG. 11). reference).

  On the other hand, if there is at least one message set with NAK in the message received during the period from slot 2 to slot 6, the protocol control means 102 determines that its message transmission has failed. (Refer to case 3 in FIG. 11), the message is retransmitted. Even when no message is received during the period from slot 2 to slot 6, the protocol control means 102 determines that its own message transmission has failed (see case 4 in FIG. 11) and retransmits the message. Further, when an abnormal message in which ACK / NAK cannot be determined is received during the period from slot 2 to slot 6, the protocol control means 102 determines that its message transmission has failed (see case 5 in FIG. 11). Resend the message.

  12 and 13 are schematic diagrams for explaining message retransmission processing by the protocol control unit 102. FIG. In FIGS. 12 and 13, messages for three cycles transmitted and received on the bus 5 are shown in time series in a communication system in which one cycle of communication is composed of six slots.

  First, in the example shown in FIG. 12, message A to message H are correctly transmitted and received in slot 1 to slot 6 of the first cycle (cycle 1) and slot 1 to slot 2 of the second cycle (cycle 2). In the ACK field of message B to message I, ACK is set in all bits. When the message I transmitted in the slot 3 of the cycle 2 is not correctly received by the (all) ECUs 1 on the receiving side, the slot 4 to the slot 6 of the subsequent cycle 2 and the third cycle (cycle 3) NAK is set to the bit corresponding to slot 3 in the ACK field of message J to message N transmitted in slots 1 to 2. The ECU 1 to which the slot 3 is assigned retransmits the message I in the slot 3 of the cycle 3 in response to the NAK set in the messages J to N.

  Next, in the example shown in FIG. 13, message A to message H are correctly transmitted and received in slot 1 to slot 6 of cycle 1 and slot 1 to slot 2 of cycle 2, and the ACK field of message B to message I is ACK is set for all bits. When the message I transmitted in the slot 3 of the cycle 2 is received by the (all) ECUs 1 on the receiving side as an abnormal message in which it is impossible to determine whether each bit of the ACK field is ACK or NAK, In subsequent slots 2 to 6 of cycle 2 and slots 1 to 3 of cycle 3, each ECU 1 could not determine the success or failure of reception according to the ACK field of message I, and therefore retransmits message D to message I. Do.

  In this way, each ECU 1 of the communication system sets success / failure of message reception from other ECUs 1 in the ACK field of the message to be transmitted, and the message of the message according to the ACK / NAK set in the ACK field of the received message. By adopting a configuration for performing retransmission, all the ECUs 1 of the communication system can reliably receive the message.

<Error control>
FIG. 14 is a chart showing a list of communication errors detected in the communication system according to the present invention. The communication protocol of the present invention detects stuff errors, CRC errors, form errors and ACK errors similar to those of the conventional CAN protocol, but does not detect bit errors detected by the conventional CAN protocol. Note that the ACK error of the communication protocol of the present invention is different in detection method from the ACK error of the conventional CAN protocol.

  In the communication protocol of the present invention, when transmitting from the SOF of the message to the CRC sequence of the CRC field in the same manner as the conventional CAN protocol, if the same signal level is 5 bits continuous, 1 bit is added to the next bit. Performs processing to add inverted data. This process is called bit stuffing. The stuffing error is an error detected when the same signal level continues for 6 bits from the SOF to the CRC sequence of the received message.

  The CRC error is an error detected when the CRC sequence value included in the received message is different from the CRC value calculated from the received message. A form error is an error that is detected for a bit whose value is fixed to either dominant or recessive (CRC delimiter and EOF) when the value of this bit in the received message differs from a fixed value.

  The ACK error is an error detected when any bit included in the ACK field of the received message is set to NAK. In the conventional CAN protocol, an ACK error is detected when a 1-bit ACK slot in a message is recessive, and if a message is received by at least one communication device in the communication system, the ACK slot is set to be dominant. Therefore, the communication device on the transmission side cannot confirm which communication device on the reception side normally receives the message and which communication device does not normally receive the message. On the other hand, in the communication protocol of the present invention, the ACK field in the message is provided with an ACK bit for each slot assigned to each ECU 1, so that the ECU 1 on the transmission side is in one cycle after transmitting its own message. By examining the ACK field of the received message, it can be individually determined whether or not the other ECU 1 has received the message normally.

  In the conventional CAN protocol, each communication device performs processing for detecting the signal level of the bus after transmitting a signal to the bus, and the signal level of the signal transmitted at this time does not match the detected signal level. If a bit error was detected. In the communication protocol of the present invention, each ECU 1 does not detect the signal level of the bus 5 after signal transmission, and therefore does not detect this bit error.

  Each ECU 1 of the communication system performs the above error detection when receiving a message from another ECU 1, and when any error is detected, a message transmitted by itself within one cycle period after the error is detected. The NACK is set to the corresponding bit of the ACK field included in the transmission and transmission is performed.

  Next, the operation of the error control means 103 included in the protocol control layer of the ECU 1 will be described. In the conventional CAN protocol, a communication device that frequently has errors and is suspected of having a failure or the like is provided with a function of stopping the message transmission / reception process and preventing the communication system from being adversely affected. The communication protocol has the same function. Such error-related control processing is performed by the error control means 103 of each ECU 1.

  The error control means 103 has two counters, a TEC (Transmit Error Counter) and a REC (Receive Error Counter) in order to count the number of occurrences of errors. FIG. 15 is a chart showing variation conditions of the error counter. Each ECU 1 gives the NAK for the self-transmitted message from all other ECUs 1 by checking the value of the bit related to the self-transmission included in the ACK field in the received message during one cycle after the transmission of its own message. If so, 8 is added to the TEC value. On the other hand, each ECU 1 is given an ACK for its own message from all other ECUs 1 and subtracts 1 from the TEC value if the message transmission is successful (however, no change occurs when TEC = 0). ).

  Each ECU 1 adds 1 to the value of REC when a form error, CRC error or stuff error is detected in the received message. Each ECU 1 detects some error in the received message, and determines to set NAK as a response to this message. However, the message that it has determined as NAK from other messages received from other ECUs 1 If the ECU 1 determines ACK, 8 is added to the value of REC.

  On the other hand, each ECU 1 checks whether or not the one message has been normally received by other ECUs 1 by checking the ACK field included in another message further received in one cycle after receiving the one message. If all other ECUs 1 have received normally, the value of REC is subtracted. At this time, each ECU 1 subtracts 1 from the value of REC if 1 ≦ REC ≦ 127, and sets the value of REC to 119 to 127 if REC> 127 (but no change when REC = 0). .

  Each ECU 1 clears the values of TEC and REC to 0 when a predetermined number of errors or more are detected and the message transmission is stopped (bus off state, which will be described later).

  FIG. 16 is a state transition diagram for explaining the operation of the error control means 103. The error control means 103 manages the state relating to error control of the ECU 1 according to the values of the two counters TEC and REC. The error control unit 103 notifies the protocol control unit 102 of these states, so that the protocol control unit 102 can perform message transmission / reception processing suitable for the error state. The states relating to error control are three states of an error active state, an error passive state, and a bus off state, and a state immediately after the ECU 1 is started (that is, an initial state) is an error active state. The values of TEC and REC are cleared to 0 when the ECU 1 is started.

  The error active state is a normal operation state of the ECU 1 and is a state in which the ECU 1 can send and receive messages without restriction. In the message transmitted by the ECU 1 in the error active state, the error active bit is set to dominant. When the TEC value exceeds 127 or the REC value exceeds 127 in the error active state, the error control means 103 makes a transition from the error active state to the error passive state.

  The error passive state is a state in which message transmission is restricted because the value of the error counter exceeds a certain value. The ECU 1 in the error active state is limited in message transmission so that message transmission related to one assigned slot is performed only once every two cycles. Thereby, the message transmission of the ECU 1 suspected of being out of order is prevented from interfering with the message transmission / reception of other ECUs 1.

  Further, the error active bit is set to recessive in the message transmitted by the ECU 1 in the error passive state. The ECU 1 that has received the message in which the error active bit is set to recessive ignores the response of this NAK even if NAK is set in the ACK field of this message (not regarded as message reception failure). To process). Even if the error active flag is set to recessive, as long as the ACK field is set to ACK, the ECU 1 receiving this message is the same as when receiving a message with normal ACK set May be performed. That is, in the communication protocol of the present invention, the error active bit in the message is set to recessive and the ACK field is set to NAK, so that this message can be used as an alternative to the error frame (passive error flag) of the conventional CAN protocol. doing.

  When both the TEC and REC values are 127 or less in the error passive state, the error control means 103 makes a transition from the error passive state to the error active state. When the TEC value exceeds 255 in the error passive state, the error control means 103 makes a transition from the error passive state to the bus off state.

  In the bus-off state, the value of the error counter further increases and exceeds a certain value, so that it is considered that the ECU 1 has reached an abnormal state such as a failure, and message transmission / reception is prohibited. For this reason, the ECU 1 in the bus-off state cannot perform any message transmission / reception until a predetermined condition for releasing the bus-off state is satisfied. When the bus-off state ECU 1 receives a request for clearing the bus-off from the application 101 to the protocol control unit 102 (when the bus-off clear condition is satisfied), the error control unit 103 makes a transition from the bus-off state to the error-active state. And clear the TEC and REC values.

  When each ECU 1 of the present invention performs the above-described error control processing, error control equivalent to the conventional CAN protocol can be realized.

<Protocol control details>
Next, details of the control processing according to the communication protocol of the present invention will be described with reference to a state transition diagram. FIG. 17 is a state transition diagram for explaining an operation related to the communication control process of the ECU 1. In the following description, “X” indicates a counter value used for start-up of communication processing. When the counter X value is reduced to 0 with the update of the slot counter, the ECU 1 Resend the message. The counter X corresponds to time measuring means for measuring the waiting time until message transmission. “N” indicates the number of slots in one cycle, and “i” indicates the minimum number among the slot numbers assigned to each ECU 1.

  In the communication protocol of the present invention, each ECU 1 makes a transition between eight operating states of an initial state, an initial abnormal state, a synchronization preparation state, a synchronization waiting state, a synchronization state, a sleep preparation state, a bus sleep state, and a bus off state, Control processing is performed. The initial state is a state before the ECU 1 starts communication, and the ECU 1 is in this state after the device is turned on (after a power-on reset) or after a reset signal is input. In the initial state, the ECU 1 acquires information (such as the number of slots and the slot number) necessary for communication by input from an external device or by reading data stored in advance and completes initial setting. Transition is made to a synchronization preparation state in order to synchronize communication with other ECUs 1. However, when an abnormality occurs in the initial state or when the initial setting fails, the ECU 1 transitions from the initial state to the initial abnormal state and stands by in the initial abnormal state.

  FIG. 18 is a flowchart showing the processing procedure of the ECU 1 in the initial state. In the flowcharts shown in FIGS. 18 to 26, exceptional processes such as a process of transitioning to an initial state when a reset signal is input and a process of transitioning to a bus off state when a bus off condition is satisfied are performed. The illustration is omitted. The processing shown in the flowcharts of FIGS. 18 to 26 is processing performed by the protocol control means 102 in the protocol control layer of the ECU 1.

  The ECU 1 that has transitioned to the initial state first obtains information such as the number of slots and the slot number and performs initial setting (step S1). Next, the ECU 1 determines whether or not an abnormality has occurred in the initial setting (step S2). If an abnormality has occurred (S2: YES), the transition designation to the initial abnormality state is designated (step S3), and the process is terminated. To do. When the initial setting is completed without any abnormality (S2: NO), the ECU 1 sets the value of the counter X to (3N) (step S4) and starts the slot count operation (step S5). A transition is made to the synchronization preparation state (step S6), and the processing in the initial state is terminated.

  The synchronization preparation state is a state for confirming whether or not another ECU 1 has already transmitted a message, and is devoted to receiving a message for a maximum of two cycles. The ECU 1 checks whether or not a message is transmitted on the bus 5, and when a message transmitted by another ECU 1 is detected, the ECU 1 performs reception processing to synchronize with this message. That is, when the message is normally received, the ECU 1 transitions to a synchronous state and performs the subsequent processing in synchronization with this message. Further, when the message cannot be normally received (when an abnormal message is received), the ECU 1 shifts to the synchronization waiting state and resets the counter “X” to wait for the reception of the normal message. . If another ECU 1 has not started sending a message and no message on the bus 5 is detected during two cycles (when the counter “X” becomes 0), the ECU 1 itself sends a message. In order to start, a transition is made to the synchronization wait state, and an ACK frame is transmitted in the synchronization wait state.

  19 and 20 are flowcharts showing the processing procedure of the ECU 1 in the synchronization preparation state. In the synchronization preparation state, the ECU 1 repeatedly performs the processing shown in FIGS. 19 and 20. The ECU 1 in the synchronization preparation state determines whether the slot has been updated (whether the slot number has changed) by checking the value of the slot counter (step S11). If the slot has not been updated, (S11: NO), waiting until the slot is updated. When the slot is updated (S11: YES), the ECU 1 subtracts 1 from the value of the counter X (step S12), and further determines whether or not the value of the counter X is 0 (step S13). When the value of the counter X is 0 (S13: YES), that is, when the value of the counter X reaches 0 without receiving a message, the ECU 1 shifts to a synchronization waiting state (step S14), and is in a synchronization ready state. The process ends. (ECU 1 transmits an ACK frame after transitioning to the synchronization wait state.)

  If the value of the counter X is not 0 (S13: NO), the ECU 1 determines whether a normal message has been received (step S17). If a normal message has not been received (S17: NO), the ECU 1 further determines whether or not an abnormal message has been received (step S20). If an abnormal message has not been received (S20: NO), that is, if no message has been received from another ECU 1, the ECU 1 ends the process (however, the illustrated process is repeated in the synchronization preparation state). The processing of the ECU 1 is returned to step S11).

  When a normal message is received (S17: YES), the ECU 1 sets the value of the counter X to (2N) (step S18), transitions to the synchronization state (step S19), and ends the process of the synchronization preparation state To do. When an abnormal message is received (S20: YES), the ECU 1 further determines whether or not the value of the counter X is larger than (N + i−2) (step S21). When the value of the counter X is larger than (N + i−2) (S21: YES), the ECU 1 sets (2N + i−2) as the value of the counter X (step S22), and transitions to a synchronization waiting state (step S23). ), And finishes the processing of the synchronization preparation state. If the value of the counter X is equal to or less than (N + i−2) (S21: NO), the ECU 1 sets the value of the counter X to (N + i−2) (step S24), and transitions to a synchronization wait state (step S24). S23), the process is terminated.

  The state of waiting for synchronization is a state of waiting for reception of a message from another ECU 1. When a message from another ECU 1 is normally received, the ECU 1 starts processing in synchronization with the received message and transitions to the synchronization state. To do. When an abnormal message is received in the synchronization waiting state, the ECU 1 waits for retransmission of this message. Further, when no message is received from another ECU 1 in the synchronization waiting state (when the counter “X” becomes 0), the ECU 1 transmits an ACK frame. Further, when the value of the counter X becomes 0 in the synchronization preparation state and the state transitions to the synchronization waiting state, the ECU 1 first transmits an ACK frame.

  FIG. 21 is a flowchart showing a processing procedure of the ECU 1 in the synchronization waiting state. The ECU 1 that has transitioned to the synchronization waiting state first checks whether or not the value of the counter X is 0 (step S30), and thereby the value of the counter X becomes 0 in the synchronization preparation state and transitions to the synchronization waiting state. Determine whether or not. When the value of the counter X is 0 (S30: YES), the ECU 1 sets (2N + i−2) as the value of the counter X (step S34), transmits an ACK frame (step S35), and proceeds to step S31. To proceed. If the value of the counter X is not 0 (S30: NO), the ECU 1 advances the process to step S31.

  In step S31, the ECU 1 waiting for synchronization determines whether or not the slot has been updated by checking the value of the slot counter (step S31). If the slot has not been updated (S31: NO). Wait until the slot is updated. When the slot is updated (S31: YES), the ECU 1 subtracts 1 from the value of the counter X (step S32), and further determines whether or not the value of the counter X is 0 (step S33). When the value of the counter X is 0 (S33: YES), the ECU 1 sets (2N + i−2) as the value of the counter X (step S34), transmits an ACK frame (step 35), and proceeds to step S31. To return.

  If the value of the counter X is not 0 (S33: NO), the ECU 1 determines whether or not a normal message has been received (step S36). If a normal message has not been received (S36: NO), the ECU 1 further determines whether or not an abnormal message has been received (step S39). If an abnormal message has not been received (S39: NO), the ECU 1 returns the process to step S31.

  When a normal message is received (S36: YES), the ECU 1 sets the value of the counter X to (2N) (step S37), transitions to the synchronization state (step S38), and finishes the process of waiting for synchronization. To do. When an abnormal message is received (S39: YES), the ECU 1 sets (N + i−2) as the value of the counter X (step S40), and returns the process to step S31.

  The synchronization state is a state in which the synchronization is established with at least one other ECU 1, and the ECU 1 transmits a message (data frame or ACK frame) in a slot assigned to itself. The synchronization state has two internal states, an error active state and an error passive state, depending on the values of TEC and REC. In the error passive state, message transmission is limited to once every two cycles. The ECU 1 operates in this synchronized state in the normal operation state. Further, when no message is received from all other ECUs 1 during two cycles, the ECU 1 transmits an ACK frame and transitions to a synchronization waiting state. When a sleep request is given from the application 101 of the application layer, the ECU 1 transitions to a sleep transition state. In addition, the ECU 1 transits to the initial state in response to the input of the reset signal, and transits to the bus off state in response to the establishment of the bus off condition.

  22 and 23 are flowcharts showing a processing procedure of the ECU 1 in the synchronized state. In the synchronized state, the ECU 1 repeatedly performs the processes shown in FIGS. 22 and 23. The synchronized ECU 1 determines whether or not a sleep instruction is given from the application 101 (step S51). If a sleep instruction is given (S51: YES), the ECU 1 transitions to the sleep preparation state (step S51). S52), the synchronization state process is terminated.

  When the sleep instruction from the application 101 is not given (S51: NO), the ECU 1 determines whether or not the action point of the slot assigned to itself has been reached (step S53). When the action point is reached (S53: YES), the ECU 1 further determines whether or not its own error state is an error passive state (step S54). When the error state is the error passive state (S54: YES), the transmission of the message is limited to once every two cycles, so the ECU 1 further determines whether or not it is a cycle in which the message itself can be transmitted (step) S55). When it is determined that the cycle is not capable of transmitting a message (S55: NO), the ECU 1 ends the process (however, the illustrated process is repeatedly performed in a synchronized state, and the process of the ECU 1 returns to step S51).

  If the error state is not an error passive state (S54: NO), that is, if the error state is error active, or if the error state is a cycle in which a message can be transmitted even if the error state is an error passive state (S55: YES), the ECU 1 It is checked whether there is data to be transmitted to another ECU 1 (step S56). When there is data to be transmitted to another ECU 1 (S56: YES), the ECU 1 generates and transmits a data frame including this data (step S57), and ends the process. If there is no data to be transmitted to another ECU 1 (S56: NO), the ECU 1 generates and transmits an ACK frame (step S58), and ends the process.

  If the action point of the slot assigned to itself has not been reached (S53: NO), the ECU 1 determines whether or not the slot has been updated by checking the value of the slot counter (step S59). If the slot has not been updated (S59: NO), the ECU 1 returns the process to step S51 and continues to steps S51, S53 and until the sleep instruction is given, the action point is reached, or the slot is updated. The determination of S59 is repeated.

  When the slot is updated (S59: YES), the ECU 1 subtracts 1 from the value of the counter X (step S60), and further determines whether or not the value of the counter X is 0 (step S61). When the value of the counter X is 0 (S61: YES), the ECU 1 sets (2N + i−2) as the value of the counter X (step S62), transmits an ACK frame (step 63), and enters the synchronization waiting state. A transition is made (step S64), and the processing of the synchronization state is terminated. If the value of the counter X is not 0 (S61: NO), the ECU 1 determines whether a normal message has been received (step S65). When a normal message is received (S65: YES), the ECU 1 sets (2N) as the value of the counter X (step S66) and ends the process. When a normal message is not received (S65: NO), that is, when an abnormal message is received or when no message is received, the ECU 1 ends the process.

  In the sleep preparation state, when a sleep request is given from the application 101 and an agreement of sleep is obtained with another ECU 1, or when the sleep request is canceled from the application 101, the ECU 1 is in another state. Transition to. In the sleep preparation state, the ECU 1 cannot transmit a data frame, but only transmits an ACK frame with the sleep bit set to recessive. When the ECU 1 receives an ACK frame in which the sleep bit is set to recessive from another ECU 1 over M (predetermined constant) cycles, the ECU 1 transits to the bus sleep state. Further, when the sleep request is canceled from the application 101, the ECU 1 shifts to a synchronous state.

  FIG. 24 is a flowchart illustrating a processing procedure of the ECU 1 in the sleep preparation state. In the illustrated process, the ECU 1 performs a process using a sleep preparation counter, and this counter is initialized to 0 at the time of initial setting or the like. The ECU 1 that has transitioned to the sleep ready state first determines whether or not the sleep request from the application 101 has been canceled (step S71). If the sleep request has not been canceled (S71: NO), another ECU It is further determined whether or not one cycle of the ACK frame has been received (step S74). When one cycle of the ACK frame has not been received (S74: NO), the ECU 1 returns the process to step S71, and the process of steps S71 and S74 is continued until the sleep request is canceled or one cycle of the ACK frame is received. Repeat the determination.

  When the sleep request is canceled by the application 101 (S71: YES), the ECU 1 sets the value of the sleep preparation counter to 0 (step S72), transitions to a synchronous state (step S73), and processing of the sleep preparation state Exit.

  When one cycle of the ACK frame is received (S74: YES), the ECU 1 increments the value of the sleep preparation counter (step S75) and determines whether or not the value of the sleep preparation counter has reached a preset value M. (Step S76). If the value of the sleep preparation counter has not reached M (S76: NO), the ECU 1 returns the process to step S71 and repeats the above process. When the value of the sleep preparation counter reaches M (S76: YES), the ECU 1 sets 0 as the value of the sleep preparation counter (step S77). Next, the ECU 1 prohibits normal sampling by the bit sampling means 106 (step S78), that is, performs power saving settings such as reducing the sampling frequency by the bit sampling means 106, and transitions to the bus sleep state (step S79). ), The sleep ready state process is terminated.

  The bus-off state is a state in which a transition is made when a bus-off condition of TEC> 255 is satisfied in all other states, and waits until the bus-off condition is cleared. When the bus-off condition is cleared, the ECU 1 transitions to the initial state.

  FIG. 25 is a flowchart showing a processing procedure of the ECU 1 in the bus-off state. When the bus-off condition of TEC> 255 is satisfied, the ECU 1 that has transitioned from another state to the bus-off state determines whether the bus-off condition is cleared (whether the bus-off condition is not satisfied) (step S81). If the bus-off condition is not cleared (S81: NO), the process waits until the bus-off condition is cleared. When the bus-off condition is cleared (S81: YES), the ECU 1 transitions to an initial state (step S82) and ends the bus-off state process.

  The bus sleep state is a state in which the ECU 1 monitors the bus 5 in a low power consumption state such as when an agreement regarding sleep with another ECU 1 is established in the communication system and the sampling frequency is reduced. In the bus sleep state, the ECU 1 does not transmit a message, and when the dominant (wake-up request) on the bus 5 is detected, or when cancellation of the sleep request is given from the application 101, the sampling frequency is set. A return process from a low power consumption state such as returning to a normal state is performed, and a transition is made to the initial state.

  FIG. 26 is a flowchart showing the processing procedure of the ECU 1 in the bus sleep state. The ECU 1 that has transitioned to the bus sleep state determines whether or not a wake-up request from the application 101 has been given (step S91), and when no wake-up request has been given (S91: NO), on the bus 5 It is further determined whether or not a dominant signal is detected (step S92). When the dominant signal is not detected (S92: NO), the ECU 1 returns the process to step S91, and repeats the determination process until a wake-up request is given or a dominant signal is detected.

  When a wake-up request is given from the application 101 (S91: YES), or when a dominant signal is detected on the bus 5 (S92: YES), the ECU 1 transits to an initial state (step S93). The bus sleep state process is terminated.

<Startup sequence>
Next, the startup sequence performed by each ECU 1 of the communication system according to the present invention will be described with reference to some examples. Each ECU 1 of the communication system according to the present invention has a three-cycle period in order to determine whether there is another ECU 1 that has already started transmitting a message after being activated and transitioned from the initial state to the synchronization preparation state. Only receive messages. When a normal message is received from another ECU 1 during this period, the ECU 1 synchronizes with the slot number included in the received message, transitions to a synchronous state, and performs normal message transmission / reception. If an abnormal message is received during this period, the ECU 1 sets the slot that received the abnormal message as the first slot (slot 1) in the cycle, transitions to the synchronization wait state, and sets a value in the counter X used as a timer. Set and wait for message resend in subsequent cycles. If a message from another ECU 1 is not received during this period, the ECU 1 transmits an ACK frame to set a value in the counter X, and waits for synchronization with the slot that has transmitted the message as the slot 1 To wait for a response from another ECU 1.

  27 to 29 are timing charts showing an example of processing of the startup sequence. The illustrated example is a start-up sequence in a communication system in which one cycle is 4 slots, and slots 1 to 4 are assigned to the ECUs 1a to 1d, respectively. In each figure, a transmission message (a rectangle in which a character string of Msg is written), an operation state (dashed oval), a slot counter value (SC =), and a counter X value (X =) are represented by ECUs 1a to 1d. Each is illustrated.

  The example shown in FIG. 27 is an example in which the startup sequence is normally performed. The ECU 1b to which the slot 2 is assigned transmits the message A at the timing of the counter X = 0 in the synchronization waiting state. This message A is normally received by the other ECUs 1a, 1c and 1d, and the slot counters of the ECUs 1a, 1c and 1d are updated in synchronization with the slot number (slot 2) included in the message A, and the ECUs 1a, 1c And 1d transition to a synchronous state.

  The ECU 1c transmits the message B in the next slot (slot 3), and the ECU 1b that has received the message B normally updates the slot counter in synchronization with the slot number (slot 3) included in the message B. Transition from wait state to synchronous state. Thereby, all the ECUs 1a to 1d can cyclically transmit the subsequent messages C to K in a state in which the values of the slot counters are synchronized.

  The example shown in FIG. 28 is an example when the ECUs 1 a and 1 b transmit messages simultaneously in the startup sequence, and two messages collide on the bus 5. When the two ECUs 1a and 1b in the synchronization waiting state have the counter X value of 0 and the messages A and B are transmitted simultaneously, the ECUs 1a and 1b that have transmitted the messages do not check the transmitted message. Therefore, it does not know that the messages A and B have collided, and sets the value of the counter X to (2N + i−2) (that is, the ECU 1a sets the value of the counter X to 7 and the ECU 1b sets the value of the counter X to Set the value to 8). Further, since the ECUs 1a and 1b that have transmitted the message regard the timing of transmitting the message as slot 1 and set the slot counter, the next slot is both slot 2.

  Further, the ECUs 1c and 1d in the synchronization preparation state that have received the collision messages A and B determine that the received message is an abnormal message, and consider the cycle in which the message is received as cycle 1 to set the value of the slot counter. At the same time, the value of the counter X is set to (2N + i−2) (that is, the ECU 1c sets the value of the counter X to 9 and the ECU 1d sets the value of the counter X to 10) and waits for synchronization. Transition to.

  In this way, when the four ECUs 1a to 1d set different values in the counter X according to the assigned slot numbers, only the ECU 1a having the counter X value of 0 first thereafter transmits the message C. It can be performed. The message C is normally received by the other ECUs 1b to 1d, and the ECUs 1b to 1d synchronize their slot counter values with the slot number (slot 1) included in the message C, and transition to the synchronized state. Thereafter, the ECU 1b transmits the message D in the next slot 2, the message D is normally received by the other ECUs 1a, 1c and 1d, and the ECU 1a in the synchronization waiting state has the slot number (slot 2) included in the message D. The slot counter is synchronized with the transition to the synchronized state.

  The example shown in FIG. 29 is another example in the case where the ECUs 1 a and 1 b transmit messages simultaneously in the startup sequence and two messages collide on the bus 5. Similarly to the example shown in FIG. 28 described above, the ECUs 1a and 1b that simultaneously transmitted messages set the value of the counter X to (2N + i−2) (that is, the ECU 1a sets the value of the counter X to 7). Then, the ECU 1b sets the value of the counter X to 8), sets the slot counter by regarding the transmission timing of the message as the slot 1.

  Further, when the ECUs 1c and 1d waiting for synchronization receive the colliding messages A and B, the ECUs 1c and 1d determine that the received message is an abnormal message, and regard the cycle in which the message is received as cycle 1 and the slot counter And the counter X is set to (N + i−2) (ie, the ECU 1c sets the counter X to 5 and the ECU 1d sets the counter X to 6).

  Thus, in the ECUs 1c and 1d that have received the abnormal message, the counter X is set to (2N + i−2) or (N + i−2) depending on whether it is in the synchronization preparation state or the synchronization wait state. That is, when an abnormal message is received in the synchronization waiting state, the counter X is set to a smaller value than when an abnormal message is received in the synchronization preparation state. Therefore, after that, the value of the counter X of the ECU 1c becomes 0 first, and the ECU 1c transmits the message C. The message C is normally received by the other ECUs 1a, 1b, and 1d, and the ECUs 1a, 1b, and 1d synchronize the values of the respective slot counters with the slot number (slot 3) included in the message C, and enter the synchronized state. Transition. Thereafter, the ECU 1d transmits the message D in the next slot 2, the message D is normally received by the other ECUs 1a to 1c, and the ECU 1c in the synchronization waiting state has a slot number (slot 4) included in the message D. Synchronize the counter and transition to the synchronized state.

  As described above, even when a message collision occurs in the startup sequence, the counters X are set to different values in the ECUs 1a to 1d in the communication system, and the ECU 1a to which the smallest value is set. By starting the next message transmission from 1d, all ECUs 1a to 1d can start communication synchronously.

<Resynchronization sequence>
Next, the resynchronization sequence performed by each ECU 1 of the communication system according to the present invention will be described with reference to some examples. The re-synchronization sequence is determined based on the judgment of each ECU 1 when each ECU 1 of the communication system has started the synchronized communication after completing the startup sequence, and the ECU 1 is not synchronized due to some communication failure or the like. Is to be performed again. Each ECU 1 transitions to a synchronization waiting state and performs resynchronization when there is no message normally received from another ECU 1 between the slot where the message is transmitted and the same slot after two cycles.

  30 to 31 are timing charts showing an example of processing of the resynchronization sequence. The example shown in the figure is a resynchronization sequence in a communication system in which one cycle has four slots and slots 1 to 4 are assigned to the ECUs 1a to 1d, one by one, as in FIGS. In each figure, a transmission message (a rectangle in which a character string of Msg is written), an operation state (dashed oval), a slot counter value (SC =), and a counter X value (X =) are represented by ECUs 1a to 1d. Each is illustrated. However, illustration of the value of the counter X when the ECUs 1a to 1d are in a synchronized state is omitted.

  The example shown in FIG. 30 is a case in which one ECU 1b is out of synchronization with the other ECUs 1a, 1c, and 1d, and the ECUs 1a and 1b transmit messages A and B simultaneously. When the slot counters of the ECUs 1a, 1c and 1d become the slot 1 and the slot counter of the ECU 1b becomes the slot 2, and the ECUs 1a and 1b simultaneously transmit the messages A and B, the other ECUs 1c and 1d have an abnormal message. Is received. In the next slot, the slot counter of the ECUs 1a, 1c and 1d is slot 2, but since the slot counter of the ECU 1b is slot 2, the message transmission of the ECU 1b is not performed.

  Thereafter, the ECU 1c transmits a message C when the slot counters of the ECUs 1a, 1c, and 1d are at the timing of the slot 3. As a result, the ECU 1b that has received the message C normally synchronizes the slot counter with the slot number included in the message C, so that all the ECUs 1a to 1d can return to the synchronized state.

  The example shown in FIG. 31 is a case where a shift occurs in the synchronization of all ECUs 1a to 1d and all the ECUs 1a to 1d transmit messages A to D simultaneously. When all the ECUs 1a to 1d transmit the messages A to D at the same time, message transmission is not performed until the next cycle, and all the ECUs 1a to 1d simultaneously receive the message E after one cycle. Send ~ H. Further, after one cycle, all ECUs 1a to 1d transmit messages I to L simultaneously in the same manner.

  When each of the ECUs 1a to 1d does not receive a message from the other ECUs 1a to 1d over the two-cycle period in this way, the value of the counter X is set to (2N + i−2) and transitions to a synchronization waiting state. . At this time, the counters X of the ECUs 1a to 1d are set to different values according to the assigned slots, and by sending a message from the ECU 1a having the smallest value in the counter X, all the ECUs 1a to 1d are transmitted. The slot counter can be synchronized and cyclic message transmission can be resumed.

  In the communication system according to the present invention having the above-described configuration, one or a plurality of slots (transmission rights) are allocated in advance to each ECU 1 in a network configuration in which a plurality of ECUs 1 are connected by a common bus 5, and Since the plurality of ECUs 1 transmit the messages cyclically in the order determined in the above, the plurality of ECUs 1 do not transmit the messages at the same time. Therefore, arbitration like the conventional CAN protocol is performed. This is unnecessary, and the communication speed can be increased.

  In addition, when transmitting a message related to one slot, each ECU 1 creates and transmits a message including information indicating success or failure of message reception related to another slot together with data to be transmitted to the other ECU 1. By adopting the configuration, it is possible to notify the other ECU 1 of the success or failure of message reception by effectively utilizing the slot assigned to itself, and to provide the other ECU 1 with its own data.

  A message transmitted by one ECU 1 is received by all other ECUs 1 connected to the bus 5, and the ECU 1 that has received the message can obtain necessary data from the data field of this message, From the ACK field, it is possible to determine whether or not the message transmitted by the device itself has been received correctly. Therefore, each ECU 1 checks the information of the ACK field included in the message received during one cycle from the previous message transmission to the next message transmission related to one slot, and the previous message is correctly received by the other ECU 1. If not, the message can be retransmitted in the next slot.

  As a result, the plurality of ECUs 1 can efficiently and efficiently perform message transmission without causing a message transmission collision, and even if the message is not correctly received due to some malfunction, the message can be reliably retransmitted. It can be performed.

  In addition, in the message that is created and transmitted by the ECU 1, each communication device includes the ACK field that includes message reception success / failure information related to a slot for one cycle. By examining each of the ACK fields, it is possible to know whether or not the transmission message has been correctly received by all other communication devices sharing the bus 5.

  In addition, when no message transmission is performed for one slot, each ECU 1 of the communication system omits the message reception process related to this slot, and performs the process related to the next slot. When the assigned ECU 1 stops message transmission for some reason, the time during which messages are not transmitted and received during the cycle can be shortened as much as possible, which contributes to an increase in communication speed.

  Further, the message created and transmitted by each ECU 1 includes slot number information for identifying which slot the message is transmitted, and each ECU 1 performs communication processing according to the slot number of the received message. With this configuration, the plurality of ECUs 1 in the communication system can reliably transmit and receive messages by synchronizing the slots.

  Each ECU 1 has a TEC and REC error counter to count the number of error occurrences related to message transmission / reception. When the number of error occurrences exceeds a predetermined number, each ECU 1 transmits a message once every two cycles. By reducing the configuration, it is possible to prevent the message transmission of the ECU 1 that is likely to have a failure or the like from adversely affecting the processing of the other ECUs 1, and to improve the reliability of the communication system.

  Further, in a startup sequence performed after startup, each ECU 1 is devoted to receiving a message from another ECU 1 for 3 cycles immediately after driving, and receives a message for 3 cycles. In the case where the process is started in synchronization with and no message is received within 3 cycles, the configuration is such that a plurality of ECUs 1 of the communication system can be surely activated after starting by transmitting the message (ACK frame). Communication processing can be started synchronously.

  In the start-up sequence, each ECU 1 sets the value of the counter X according to the slot number assigned to itself after sending a message and receiving an abnormal message, and decrements the counter X to reach 0. By adopting a configuration for performing message transmission, a plurality of ECUs 1 in the communication system can set different values in the counter X, and the ECU 1 with the smallest value can independently perform the next message transmission. Therefore, the other ECU 1 can receive this message and perform synchronization.

  In addition, in response to a malfunction (synchronization shift) after the start-up sequence is completed and synchronization is established, each ECU 1 is assigned to itself if no message is received from another ECU 1 during two cycles. By setting the value of the counter X in accordance with the slot number and performing the resynchronization by the same process as the startup sequence, a synchronization shift occurs in a plurality of communication devices due to a communication failure or the like. Even when the message transmission is performed simultaneously, a plurality of communication devices can be resynchronized reliably.

  When the communication system shifts to the sleep mode, each ECU 1 transmits and receives an ACK frame with the sleep bit set to recessive as a sleep request, and each ECU 1 receives a sleep request for all slots in one cycle. Each ECU 1 sleeps after an agreement is reached between all ECUs 1 connected to the bus 5 to shift to the sleep mode by stopping the message transmission and shifting to the sleep mode (bus sleep state). You can enter mode.

  As described above, the communication system of the present invention has substantially the same function as the function of the conventional CAN protocol, and these are realized by the protocol control layer of each ECU 1, so that it corresponds to the conventional CAN protocol. It is possible to use the application created in this way as it is (or to use the application with minor modifications). In addition, the communication system of the present invention does not need to perform arbitration like the conventional CAN protocol, and does not need to detect the signal level for each bit at the time of message transmission. Thus, message transmission / reception at a higher speed than the conventional CAN protocol can be realized.

  In the present embodiment, the slot assignment to each ECU 1 is statically performed. However, the present invention is not limited to this, and the slot assignment to each ECU 1 is activated at some timing such as after the communication system is activated. It is good also as a structure performed automatically. Further, although a plurality of slots can be assigned to one ECU 1, the present invention is not limited to this, and only one slot may be assigned to one ECU 1. The communication system of the present invention is not limited to the one mounted on the vehicle, but can be applied to other various systems.

(Modification)
Moreover, the structure of the message which ECU1 transmits / receives is not restricted to what was shown in FIG. 4, For example, the other structure as shown in the following modifications may be sufficient. FIG. 32 is a schematic diagram illustrating a message configuration of a communication system according to a modification. In this figure, only the configuration of the data frame is shown, and the ACK frame has the same configuration (configuration in which the data field is removed from the data frame), and thus illustration is omitted.

  The data frame of the modified example has a configuration in which a slot number CRC (simply described as CRC in FIG. 32) is added between the slot number and the data field with respect to the data frame shown in FIG. Although not shown, the ACK frame adds a slot number CRC between the slot number and the CRC field. The slot number CRC is used to detect an error in the slot number included in the received message, and is obtained by performing an operation using a predetermined generator polynomial on the value of the slot number. The ECU 1 that has received the message can perform error detection by comparing the value calculated by the generator polynomial from the slot number included in the received message with the value of the slot number CRC of the received message. If the two values do not match, it is determined that an error has occurred.

  In this way, by providing a slot number CRC for detecting an error in the slot number in a message transmitted and received by the ECU 1, when an error is detected in the error detection based on the CRC field, the ECU 1 It can be further checked whether it is included in the number. As a result, even when each ECU 1 receives a message including an error, if the slot number does not include an error, each ECU 1 can perform communication synchronization processing using the slot number of the received message. It is possible to smoothly perform cyclic message transmission / reception by the ECU 1.

  In the above-described modification, the slot number CRC for detecting the slot number error is provided in the message. However, the present invention is not limited to this, and data that can correct the slot number error is stored in the message. It is good also as a structure provided in.

1, 1a-1d ECU (communication device)
5 bus (communication line)
DESCRIPTION OF SYMBOLS 11 Control part 12 Input part 13 Output part 14 Storage part 15 Power supply circuit 16 Communication part 101 Application 102 Protocol control means (Message transmission means, Message re-transmission means, Communication start means, Communication resumption means, Communication stop request transmission means, Communication stop Request receiving means, communication stop control means)
103 Error control means 104 Message generation means 105 Slot management means 106 Bit sampling means 107 Bus driver

Claims (11)

In a communication system in which three or more communication devices are connected by a common communication line, and a plurality of other communication devices receive a message transmitted by one communication device.
One or a plurality of transmission rights are pre-assigned to each communication device, and the three or more communication devices transmit messages cyclically in the order determined for each transmission right,
The communication device
A plurality of reception success / failure information respectively indicating success / failure of message reception related to each transmission right, and message transmission means for generating and transmitting a message including data to be transmitted to another communication device;
Message resending means for resending a message according to reception success / failure information included in a message received from another communication device ;
If a message is not transmitted over a predetermined cycle after startup and a message is received from another communication device during the predetermined cycle, the subsequent message transmission is performed in synchronization with the message, and the predetermined cycle A communication system comprising: a communication start unit that transmits a message when no message is received from another communication device in between, and starts message transmission / reception with the other communication device . The communication device has time measuring means for measuring a waiting time until message transmission,
The communication start means of the communication device, when performing message transmission or when receiving an abnormal message from another communication device during the predetermined cycle, the time measuring means according to the assigned transmission right After measuring the time, send a message,
Communication system according to claim 1 in which a plurality of said communication device, characterized in that you have to be timing the different waiting times at the clock means. In a communication system in which three or more communication devices are connected by a common communication line, and a plurality of other communication devices receive a message transmitted by one communication device.
One or a plurality of transmission rights are pre-assigned to each communication device, and the three or more communication devices transmit messages cyclically in the order determined for each transmission right,
The communication device
A plurality of reception success / failure information respectively indicating success / failure of message reception related to each transmission right, and message transmission means for generating and transmitting a message including data to be transmitted to another communication device;
Message resending means for resending a message according to reception success / failure information included in a message received from another communication device;
A timing means for timing the waiting time until message transmission;
A communication resumption means for resuming message transmission after measuring the waiting time according to the assigned transmission right when not receiving a message from another communication device during a predetermined cycle,
The plurality of communication devices, communication systems that characterized that you have to be timing the different waiting times respectively by the clock means. In a communication system in which three or more communication devices are connected by a common communication line, and a plurality of other communication devices receive a message transmitted by one communication device.
One or a plurality of transmission rights are pre-assigned to each communication device, and the three or more communication devices transmit messages cyclically in the order determined for each transmission right,
The communication device
A plurality of reception success / failure information respectively indicating success / failure of message reception related to each transmission right, and message transmission means for generating and transmitting a message including data to be transmitted to another communication device;
Message resending means for resending a message according to reception success / failure information included in a message received from another communication device;
A communication stop request transmitting means for transmitting a message requesting to stop message transmission;
A communication stop request receiving means for receiving a message requesting to stop communication processing from another communication device;
Communication stop control means for stopping message transmission when the communication stop request receiving means receives a message requesting to stop communication processing from a plurality of other communication devices over a predetermined cycle. to that communication system. The message transmitting means of the communication device determines whether or not the reception of the message related to another transmission right transmitted during one cycle from the previous message transmission related to the one transmission right to the current message transmission is received. The communication system according to any one of claims 1 to 4, wherein the communication system includes a message to be transmitted as success / failure information. Each communication device is configured to transmit or receive a message related to a next communication right when a message related to one communication right is not transmitted for a predetermined time. or communication system according to any one of claims 5. The message transmitting means of the communication device generates and transmits a message including identification information for identifying a transmission right,
The communication system according to any one of claims 1 to 6 , wherein each communication device is configured to synchronize message transmission and reception based on the identification information of the received message. The communication system according to claim 7 , wherein the message transmission unit of the communication device generates and transmits a message including information for detecting or correcting an error in the identification information. The communication device has an error counter that counts the number of occurrences of errors related to message transmission and reception,
It said message sending means of the communication device, when the number of errors that the error counter has counted exceeds a predetermined value, according to claim 1 to claim 8, characterized in that you have to reduce the frequency of message transmission The communication system according to any one of the above. In a communication device that transmits and receives messages to and from two or more other devices via a common communication line,
One or more transmission rights are pre-assigned,
Message transmission for generating and transmitting a message including a plurality of pieces of reception success / failure information indicating success / failure of message reception related to each transmission right including transmission right assigned to another device and data to be transmitted to the other device Means,
Message resending means for resending the message according to the reception success / failure information included in the message received from another device ;
When a message is not transmitted over a predetermined cycle after startup and a message is received from another device during the predetermined cycle, subsequent message transmission is performed in synchronization with the message, and during the predetermined cycle Communication start means for transmitting a message when no message is received from the other device and starting message transmission / reception with the other device ,
The message transmitting means and the message retransmitting means are configured to cyclically transmit messages to and from the other apparatus in the order determined by the assigned transmission right. apparatus. In a communication device that transmits and receives messages to and from two or more other devices via a common communication line,
One or more transmission rights are pre-assigned,
Message transmission for generating and transmitting a message including a plurality of pieces of reception success / failure information indicating success / failure of message reception related to each transmission right including transmission right assigned to another device and data to be transmitted to the other device Means,
Message resending means for resending the message according to the reception success / failure information included in the message received from another device;
A communication stop request transmitting means for transmitting a message requesting to stop message transmission;
Communication stop request receiving means for receiving a message requesting to stop communication processing from another device;
Communication stop control means for stopping message transmission when the communication stop request receiving means receives a message requesting to stop communication processing from a plurality of other devices over a predetermined cycle;
With
The message transmission unit and the message retransmission unit are configured to cyclically transmit messages to and from the other device in the order determined by the assigned transmission right.
A communication device characterized by the above.

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